Haven't done butternut on the smoker yet. When I do it in the oven, I cut em in half, clean, and put them cut side up for the duration. Take them out when they are soft. Use a small skewer to check. It's been a while, (last fall), but if memory serves, it takes about an hour at 350*. Since yours is smaller, I'm guessing about an hour & 1/2 - 2 hours on the smoker.

i haven't done a butternut in the smoker before, but i cook them in my weber kettle all the time. i always cut them in half (an easy way to do this is with a meat cleaver and mallot) and then cleaned out the seeds. then i put a dab of butter into each and a rounded teaspoon of brown sugar. after that i cook indirectly in moderate heat for about 40 minutes.

add or subtract time depending on your cooking environment. you'll know when there done because the will be soft to the touch.